Question

Bart practices his trumpet 1 1/4 hours each day. How many hours will he practice in 6 days?

Answer 1

Bart will practice in total 7 hrs and 30 mins in the time spam of 6 days

Answer 2

The question is basically asking "What is 1¼ × 6?"
There are multiple ways to arrive at a solution for this.
The first is to break the 1¼ into parts.
1¼ = 1 + ¼. When we multiply 1¼ by 6, that's equal to 1×6 + ¼×6.
1×6 = 6.
¼×6 = 6/4 = 1½.
6 + 1½ = 7½ hours 

You could also put 1¼ as an improper fraction and then multiply.
1¼ = 1 + ¼.
1 = 4/4.
4/4 + 1/4 = 5/4.
5/4 × 6 = (5×6)/4 = 30/4.
30/4 = 15/2 = 7½ hours